This makes me feel foolish.
In[1]:=Needs["Statistics`DiscreteDistributions`"]
In[2]:=Plot[PDF[BinomialDistribution[101,u],26],{u,0,0.5},PlotRange->All]
This gives me a nice, bell-shaped curve, with a minimum of about 0 and a
maximum of about .09. Let's integrate it from 0 to .29.
In[3]:=Integrate[PDF[BinomialDistribution[101,u],26],{u,0,.29}]
Out[3]=-0.612253
How can this be negative?